Evaluation of the power system reliability if a nuclear power plant is replaced with wind power plants

doi:10.1016/j.ress.2019.01.010

Reliability Engineering & System Safety

Volume 185, May 2019, Pages 455-464

https://doi.org/10.1016/j.ress.2019.01.010 Get rights and content

Highlights

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Method for evaluation of power system reliability if nuclear is replaced with wind power plants.
•
Upgrade of the loss of load expectation method with consideration of the actual instead of the nominal power.
•
Semi dynamic considerations of evaluations, which are performed for every hour of system operation instead of performing one run.
•
Development of new models and application of real case studies.

Abstract

The modern power systems include a larger number of more dispersed and smaller power generating sources, which are slowly replacing larger and more concentrated power sources. The objective of this paper is to analyse the replacement of nuclear power plant with wind power plants to compare both cases from the viewpoints of power system reliability. The load diagram and the variability of the power plants, whose power depend on the environmental parameters with the time is considered. This paper is focused on the loss of load expectation. The upgraded method considers plant power as a function of the time instead of its nominal power. Initial real power system model consists of twelve power plants including one nuclear power plant. This plant is then replaced by three wind power plants with their total power five times larger than the power of the nuclear power plant. A comparison of reliability in terms of comparing the loss of load expectation is performed using the real weather data for one calendar year. The results show that the replacement of the nuclear power plant with several wind power plants with wind power capacity five times larger than the nuclear power capacity causes a decrease of the power system reliability.

Introduction

The modern power systems include a larger number of more dispersed and smaller power generating sources, which are slowly replacing larger and more concentrated power sources [1]. Consequently, the power system operators deal with more dynamic conditions, larger number of parameters under investigation and more complex solutions requiring more complex models and new analyses. The capacity factors have been studied on real weather data for offshore wind power plants compared to onshore plants showing higher values for the offshore plants [2]. The reliability of equipment integrated in wind power plants has been studied identifying more and less reliable subassemblies [3]. In parallel, the analyses of faults in the more and more interconnected transmission power systems hae been conducted to asses the total energy not supplied, the total loss of power, the restoration time and several other power reliability indicators, because the power system is too complex that the reliability would be represented as one parameter [4]. Weather parameters have been studied to enable more certain predictions of available power from power technologies, which power is linked to the weather parameters [5]. Many similar analyses and trends pave the way of more and more wind power in power systems.

The objective of this paper is to analyse replacement of nuclear power plant with wind power plants in order to compare both cases from the viewpoint of power system reliability. The characteristics of the real power system needs to be considered including the features of the load diagram and the variability of the power of wind and hydro power plants, whose power depend on the environmental parameters.

Reliability of the power systems is a wide term and a large number of methods are developed, each of which represents the power system reliability from each side [6], [7], [8], [9]. They can be grouped into two main groups.

The first one deals with the power system as a static system where the term adequacy is considered as a measure of the static power system reliability. The method was developed to enable assessment of power system reserve keeping in mind the loss of load probability [10]. The common mechanisms of dependent failures were introduced to the method, which enabled consideration of events, which can cause the failures of more components due to the same root cause [11]. The method was improved to evaluate time dependent power system reserve considering timely changing daily power diagram with respect to desired level of system reliability [12]. The importance factors have been identified in order to distinguish more and less important power generation sources in the power system from the reliability point of view [13]. The data collection processes about the consumer oriented indices on the distribution power system were conducted in parallel to develop more indicators, each showing the power system reliability from another viewpoint [14].

The other group deals with the power system as a dynamic system where the term security is considered as a measure of the dynamic power system reliability [15]. The inertia in the power system is studied together with the frequency response in order to keep the power system stable [16]. And, the improved methods have been developed for simulations of power flows through the lines of the power system considering the system dynamics [17]. Both groups also represent the standpoint for a variety of simulation and optimisation methods which improve the power system planning processes and its operation. The method was developed to schedule the power from a variety of power plants in the power system considering the environmental characteristics and the availability of the power generators included [18].

The outline of the paper is the following. The section about methods describes the loss of load expectation as an existing method in theory and in terms of a simple example. Its upgrade is presented and the computer code, which is developed as a support, is described. The Section 3 presents the models:

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the initial power system model with a nuclear power plant (no wind power considered),
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the power system model without the nuclear power plant and with three wind power plants:
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  the real weather data is used in the first case,
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  the random wind speed data is used in other cases, where the average of the random wind speed is notably higher then the average wind speed of the real weather data.

Section 4 gives the takeaway message.

Section snippets

Methods

The focus of this paper is placed on the first of the two sets of methods for the evaluation of the power system reliability which considers the power system as a static one and thus excludes dynamic stability studies [7], [9], [10]. However, consideration of the actual instead of the nominal capacity of the intermittent power sources is considered in the paper, i.e. the capacity of the hydro power plants depending on the river flows, and, i.e. the capacity of the wind power plants depending on

Power system model

The data for the power system consists of the identification of each plant, its nominal power capacity (net electric power delivered to the power system), and its forced outage rate (or plant unavailability caused by unintentional causes). From this, the availability needs to be obtained for LOLE calculation. For the renewable sources such as hydro power plants, the functions of their power capacity versus time depend on the hourly river flow. The functions of power capacity versus time based

Conclusions

The objective of the work was to analyse the replacement of conventional power plant with weather dependent renewable power plants. In other words, the objective was to analyse the replacement of nuclear power plant with several wind power plants.

The methods of static power system reliability were considered and the loss of load expectation was selected for its improvement. The method was improved in order to allow the consideration of variability of power versus weather parameters in power

Acknowledgment

The Slovenian Research Agency partially supported this research within the research program P2-0356.

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Citation Excerpt :
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View full text

Evaluation of the power system reliability if a nuclear power plant is replaced with wind power plants

Highlights

Abstract

Introduction

Section snippets

Methods

Power system model

Conclusions

Acknowledgment

Int J Electr Power Energy Syst

Electricity markets, reliability and the evolving U.S. power system

Anal Group

Capacity value of offshore wind in Great Britain

Proc Inst Mech Eng, Part O

Comparisons of offshore wind turbine reliability

Proc Inst Mech Eng, Part O

European power grid reliability indicators, what do they really tell?

Electric Power Syst Res

Modelling weather dependence in online reliability assessment of power systems

Proc Inst Mech Eng, Part O

Probability concepts in electric power systems

Reliability evaluation of power systems

New computational methods in power system reliability

Assessment of power system reliability

Generating reserve capacity determined by the probability method

AIEE Trans

An improved method for power system generation reliability assessment (in Slovenian)

Electrotech Rev

Estimating the additional operating reserve in power systems with installed renewable energy sources

Int J Electr Power Energy Syst

New importance factors in electric power systems (in Slovenian)

Electrotech Rev

Guide for electric power distribution reliability indices

IEEE